Simulation and modeling software typically allows a model operator to perform simulation operations over a specified time interval, each simulation operation utilizing specified inputs (e.g., rate constants and initial conditions) to generate specific outputs over the time interval for the operation. However, prior art simulation models, and interfaces for specifying simulations operations performed by such simulation models, do not provide a convenient mechanism for specifying a sequence of simulation operations whereby each operation in that sequence may employ varying inputs (e.g., rate constants) or a resetting of the state (initial conditions) of the modeled system.